On Tue, Feb 16, 2016 at 10:08 AM, <[email protected]> wrote:
> Thank Jakob.
>
> Consider much more easier function:
>
>
> function foo(o) {
> return o.x;
> }
>
>
> print(foo(37));
>
>
> listing <http://pastebin.com/u0ZM8C3w>
>
> I've got two question:
> 1) 0x36c28f53eecf 47 e8cc92fdff call 0x36c28f5181a0 ;; code:
> contextual, LOAD_IC, GENERIC
> Does that code create new IC stub? Where is the check for IC placed?
>
That's the call to the IC stub. The stub is created elsewhere (dynamically,
as needed). All the type checks happen inside the stub, not in the
enclosing function.
>
> I believe that check should looks like:
> if (actual_type1 == int) -> generate IC stub for int, if it exists then we
> call it
> if (actual_type1 == double) ...
>
More like:
if (hidden class of o == previously seen hidden class) { call previously
generated handler }
else miss /* call into C++ to create a new handler for the new hidden class
*/
At least that's the standard "monomorphic" case. The IC system is quite
flexible, each IC can be in one of many different states.
> 2) How to remove lines that looks like debug *. For example : debug:
> statement 19
>
They're just comments, part of the --code-comments output. Their purpose is
to make it easier for you to trace machine instructions back to the
JavaScript source.
> On Tuesday, February 16, 2016 at 2:31:58 PM UTC+6, Jakob Kummerow wrote:
>>
>> On Tue, Feb 16, 2016 at 8:10 AM, <[email protected]> wrote:
>>
>>> Thank Ben, but I need to some example:
>>>
>>> function add(a, b) {
>>> return a + b;
>>> }
>>>
>>>
>>> print(add(37, 73));
>>> I execute this code via d8.
>>>
>>> What is context in that case?
>>>
>>
>> Your function "add" is so simple that it doesn't need a context, and
>> indeed no context is allocated.
>>
>>
>>> I've got the asm listing via --print-code: listing
>>> <http://pastebin.com/NhWyhRDK>
>>> Actually I can't understand why the listing consists so many codes? The
>>> adder function is very simple.
>>>
>>> 0xda955b3eff6 150 49ba0000000025000000 REX.W movq r10,0x2500000000
>>> 0xda955b3f000 160 4152 push r10
>>> 0xda955b3f002 162 49ba0000000049000000 REX.W movq r10,0x4900000000
>>> 0xda955b3f00c 172 4152 push r10
>>> 0xda955b3f00e 174 48ba0000000007000000 REX.W movq rdx,0x700000000
>>> 0xda955b3f018 184 488b7c2418 REX.W movq rdi,[rsp+0x18]
>>> 0xda955b3f01d 189 e85efcffff call 0xda955b3ec80 ;; code:
>>> CALL_IC, GENERIC
>>> 0xda955b3f022 194 488b75f8 REX.W movq rsi,[rbp-0x8]
>>> 0xda955b3f026 198 48890424 REX.W movq [rsp],rax
>>>
>>>
>> ^ That's the compiled top-level code. The compiled code for function
>> "add" is in lines 109 - 170 in your pastebin. You can tell either by
>> looking at the "--- Raw source ---" section, or at the "name = add" line.
>>
>> If you run with --code-comments, you'll get comments embedded into the
>> code that'll explain what each section was generated for.
>>
>>
>>> On Monday, February 15, 2016 at 11:14:58 PM UTC+6, Ben Noordhuis wrote:
>>>
>>>> On Mon, Feb 15, 2016 at 1:57 PM, <[email protected]> wrote:
>>>> > Hi all!
>>>> >
>>>> > I'm trying to understand the full-codegen compiler in v8.
>>>> >
>>>> > Ok, I've taken the full-codegen code for x64 architecture.
>>>> >
>>>> > As I can see in code, it does following things:
>>>> > Build x64 frame
>>>> > Allocate locals
>>>> > And then allocate context <- this is magic for me
>>>> >
>>>> > The code's:
>>>> >
>>>> > // Possibly allocate a local context.
>>>> >
>>>> > if (info->scope()->num_heap_slots() > 0) {
>>>> >
>>>> > Comment cmnt(masm_, "[ Allocate context");
>>>> >
>>>> > bool need_write_barrier = true;
>>>> >
>>>> > int slots = info->scope()->num_heap_slots() -
>>>> > Context::MIN_CONTEXT_SLOTS;
>>>> >
>>>> > // Argument to NewContext is the function, which is still in rdi.
>>>> >
>>>> > ...
>>>> >
>>>> >
>>>> > What does the full-codegen does here?
>>>>
>>>> The context it allocates is the storage for a function's free
>>>> variables. V8's garbage collector is generational; the write barrier
>>>> is for tracking object references from the old space to the new space.
>>>>
>>> --
>>>
>>
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